Carbon deposition and sulfur poisoning during CO2 electrolysis in nickel based solid oxide cell electrodes

JOURNAL OF POWER SOURCES

卷:373

Article

Skafte, Theis Loye^1,2  Blennow, Peter¹  Hjelm, Johan²  Graves, Christopher² 

[1] Haldor Topsoe Res Labs, Haldor Topsoes Alle 1, DK-2800 Lyngby, Denmark

[2] Tech Univ Denmark, Dept Energy Convers & Storage, Riso Campus,Frederiksborgvej 399, DK-4000 Roskilde, Denmark

关键词: High temperature electrolysis;    CO2 reduction;    Carbon formation;    Sulfur poisoning;    Electrode gradients;    Mitigation;   

DOI  :  10.1016/j.jpowsour.2017.10.097

来源: Elsevier

【 摘 要 】

Reduction of CO2 to CO and O-2 in the solid oxide electrolysis cell (SOEC) has the potential to play a crucial role in closing the CO2 loop. Carbon deposition in nickel-based cells is however fatal and must be considered during CO2 electrolysis. Here, the effect of operating parameters is investigated systematically using simple current potential experiments. Due to variations of local conditions, it is shown that higher current density and lower fuel electrode porosity will cause local carbon formation at the electrochemical reaction sites despite operating with a CO outlet concentration outside the thermodynamic carbon formation region. Attempts at mitigating the issue by coating the composite nickel/yttria-stabilized zirconia electrode with 'carbon-inhibiting nanoparticles and by sulfur passivation proved unsuccessful. Increasing the fuel electrode porosity is shown to mitigate the problem, but only to a certain extent. This work shows that a typical SOEC stack converting CO2 to CO and O-2 is limited to as little as 15-45% conversion due to risk of carbon formation. Furthermore, cells operated in CO2-electrolysis mode are poisoned by reactant gases containing ppb-levels of sulfur, in contrast to ppm-levels for operation in fuel cell mode.

【 授权许可】

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